Application and study on preparation of bio-asphalt by modified phenolic resin from corn straw tar.

XPS, GPC, FT-IR, and GC-MS analyses were conducted on corn straw tar and 70# petroleum asphalt. The results indicate that the sulfur content in corn straw tar is lower than that in petroleum asphalt, potentially mitigating the volatilization of harmful substances upon substituting petroleum asphalt. This finding serves as evidence for the substantial presence of phenolic substances in corn straw tar. Upon employing the BOX-Behnken response surface analysis and utilizing resin yield as the evaluation index, the significance of three factors was established as follows: reaction time > phenol molar ratio > straw tar content. Based on the secondary multiple regression model, the optimal conditions for synthetic resin production are a phenolic mole ratio of 0.8, a reaction time of 125 min, and a straw tar dosage of 10 %. An assessment of resin viscosity at different VI temperatures reveals that corn stover tar can partially replace phenol and formaldehyde in the condensation reaction. Additionally, viscosity improvement is observed at elevated temperatures. Thermal gravimetric(TG) spectroscopy indicates lower mass loss in B-PF resin at high temperatures compared to PF resin or corn stover tar. In the evaluation of biological bitumen performance, it is discerned that the mixing amount of the prepared biological bitumen should be controlled at approximately 10 % of its performance. This ensures optimal efficacy without adversely affecting the performance of petroleum bitumen.

Optimization of hydroxylating DHEA to 7alpha,15alpha-diOH-DHEA by compound mutation and fermentation optimization / 生物工程学报

Combined with method of ketoconazole resistance screening, a 7alpha,15alpha-diOH-DHEA high-producing mutant Colletotrichum lini ST-1 was obtained by compound mutation of NTG and low energy N+ ion beam implantation. With the substrate concentration of 10 g/L DHEA, the molar yield of 7alpha,15alpha-diOH-DHEA reached 34.2%, increased by 46.2% than that of the original strain. Then we optimized the medium. First, Plackett-Burman design was used to evaluate the effects of medium components on molar yield of the product. Results show that glucose, yeast extract and MgSO4 x 7H2O were the important parameters for the biotransformation process. Subsequently, the path of steepest ascent was used to approach the optimal levels. To obtain the optimal levels, central composite design and response surface analysis were carried out. The optimal medium was as follows (g/L): glucose 26.34, yeast extract 12.15, corn flour 3.00, FeSO4 x 7H2O 0.015, MgSO4 x 7H2O 0.14, KH2PO4 0.90. Under the optimal conditions, the molar yield of 7alpha,15alpha-diOH-DHEA reached 49.3%, which was 44.2% higher than that of using the medium before optimization.